1. Field of the Invention
The invention relates to an imaging apparatus.
2. Description of Related Art
In the related art, a technique of retrieving a region in an image acquired continuously over time, which has characteristic information similar to characteristic information of a subject selected first to thereby track the position of the subject, is known. For example, Japanese Patent Application Publication No. 2007-272732A discloses a technique which adds a positional correction input from a user to the tracking position of a subject while performing the tracking of the subject.
According to the technique, when a plurality of regions having the characteristic Information similar to the characteristic information of the subject selected first is included in the retrieval target image acquired later, an imaging apparatus may extract a plurality of similar regions from the image as tracking positions. Thus, it may be difficult to determine one tracking position, and there is a problem in that a plurality of tracking positions may be displayed alternately.
A situation when a concrete problem occurs will be described with reference to FIGS. 6A and 6B. A case where a train having a uniformly colored front is coming towards a viewer will be described as an example. A photographer selects a focus point on which the photographer wants to focus in advance from a plurality of rectangular regions (called focus points) displayed on a finder screen as shown in FIG. 7 and stores the information thereof in a RAM of an imaging apparatus. Then, the imaging apparatus can continuously focus on a moving subject by focusing on a subject imaged at the selected focus point.
The photographer adjusts the position of a predetermined focus point on a screen while looking at the finder so as to match a position below the front window of the train which is the location of a subject being tracked first. When the two positions match each other, the photographer half-presses a shutter button. While the shutter button is being half-pressed, the imaging apparatus automatically changes the focus point and continuously performs focusing following the movement of the subject.
The imaging apparatus stores image characteristic information (for example, color information) as a template within an initial focus detection position 82a depicted by a bold frame in FIG. 6A. The color within the bold frame is divided into 3-by-3 blocks, and the averages of the R, G, and B values within the respective blocks are used as the color information. That is, the image characteristic information within the initial focus detection position 82a is expressed as 27 kinds of data (R11, G11, B11) to (R33, G33, B33), for example. The imaging apparatus calculates and tracks a portion similar to the stored template information in the next tracking image.